Welsh Liberal Democrats and their predecessors the Liberals have never benefited from entering coalitions with other parties, a new book has concluded.

In The Welsh Liberals, Professor Russell Deacon of the University of Wales writes: “At a local government and Welsh Assembly level, it seems [being in coalition] makes very little difference to the party’s electoral fortunes.

“Coalitions at the Westminster level, however, have always weakened the party in Wales, sometimes considerably.

“The various coalitions that the Welsh Liberals had with the Conservatives between 1916 and 1945 saw the Liberal vote collapse and the party marginalised to rural Wales.

“The Lib-Lab pact of the late 1970s similarly saw the party decimated across Wales. The most recent coalition with the Conservatives at Westminster has also seen the party lose much of its Welsh support at elections.

“From each coalition it has taken around a decade or more for the party to rebuild its strength and this may well be the case after the 2015 Westminster election.”

Prof Deacon told us: “There was a big debate in the party in 2000 about whether it was the right thing to do to go into coalition with Labour at the Assembly. Some people were predicting it would give the party a great platform from which to gain extra support, while others thought it would be disastrous. In the event, it didn’t seem to have any effect at all – people were indifferent about it.

“In fact, that indifference was the best outcome of any coalition entered into by the party on its fortunes in Wales. Even though it wasn’t a formal coalition, the Lib-Lab pact of the late 1970s had a disastrous outcome for the party in Wales, reducing it to just one seat.

“Earlier in the 20th century the party’s involvement in the First World War coalition and the national governments also played a part in its decline.”

Prof Deacon said that while in England, the Liberals and then the Liberal Democrats had been beneficiaries of protest votes, that hadn’t happened to anywhere near the same extent in Wales.

“The problem for the party in Wales is the existence of Plaid Cymru, which has been able on occasions to mobilise protest votes that otherwise might have gone to the Liberal Democrats.

“The Brecon and Radnor by-election in 1985 did see the Liberal Democrats able to break through, and support in that seat has been sustained very well ever since with two successive MPs, Richard Livsey and Roger Williams.

“In 1983, at the time of the SDP-Liberal Alliance, there was a real possibility of a breakthrough in Cardiff North, where there was a by-election due. But Margaret Thatcher called a general election, so the by-election never took place.”

Prof Deacon, who himself is a former Liberal Democrat councillor in Rhondda Cynon Taf, said that in his view it would be very difficult for the Welsh Liberal Democrats to say they had gained much from the current coalition at Westminster.

“They’ve had only two junior ministers – Jenny Willott and Baroness Jenny Randerson – and haven’t played a major role in the coalition. The best outcome they could hope for would be for the Silk Commission recommendation that the number of AMs should go up to 80 to be put through. That’s what they should be arguing for, because it would give the party the opportunity to get some more elected representatives in Wales who could make a difference.”